Production of mono-filaments



Patented June 15, 1943 PRODUCTION OF MONO-FILAMENTS Karl Heymann, Meadville, Pa., assignor to American Viscose Corporation, Wilmington, Del., a

corporation of Delaware No Drawing. Application October 1, 1941, Serial No. 413,242

19 Claims.

This invention relates to improved methods of producing mono-filaments from a plurality of thermoplastic filaments associated in the form of a bundle.'

In accordance with prior practices, it has been common to employ solvents and/or heat to effect the fusion of filamentary bundles into the form of a unitary filament, commonly called monofils or mono-filaments. In such processes, it is difficult to pre-determine the diameter of the monofilament produced because of the excessive contraction in diameter of the bundle of filaments entering into the production of the monofil. In addition, the cross-section of the monofils produced thereby is rather irregular in size and shape unless additional devices, such as dies, are employed to control the final result. Furthermore, the necessity for the removal and recovery of sblvent, by vol'atilization and condensation, increases the expensiveness of such processes.

In accordance with this invention, a bundle of filamentary material of thermoplastic nature which has been stretched at some time during its production is converted directly by heating into a unitary filament having for practical purposes and to all appearances the structure of a true mono-filament. While the terms monofil and mono-filament are used in the specification to describe the unitary filament obtained in accordance with the methods herein disclosed, it is to be understood that these expressions are to include not only true monofils but also such structures as have the outward appearances and characteristics practically indicative of substantially true mono-filaments even though special rupturing procedures may indicate that the structures are composed of numerous filaments or fibers not entirely coalesced along their lengths into absolutely true mono-filaments. The expression unitary filament used in the claims is to be construed in a correspondingly broad sense to include both true and practical mono-filaments.

The thermoplastic filaments may be composed of such vinyl resins as the copolymers of vinyl acetate. and vinyl chloride, chlorinated copolymers of vinyl acetate and vinyl chloride, polyvinyl chloride and chlorinated polyvinyl chloride. When the word bundle is employed in the specification and claims hereinafter, it is intended to include groups of filaments associated in any manner, such-as tows, continuous filament yarns, or plied yams. Preferably, the bundle is formed with a certain amount of twist. This may amount to only a fraction of one turn per inch or up to as high as about 15 turns per inch. This twist serves to maintain a fair degree of uniformity in the bulkiness along the length of the bundle during treatment and hence contributes to the uniformity of the monofil along its length. Preferably a twist of from 3 to 10 turns per inch is employed to obtain the greatest uniformity and resistance to abrasion in the product. However, the twist most advantageously employed depends upon the denier of the bundle to a certain extent. For example, a twist from '7 to 10 turns per inch has been found the most desirable for producing smaller monofils up to about 400 denier while the most desirable amount of twist is less in producing heavier monofils of higher denier. The twist may be present in a singles yarn or it may be the resultant of a composite of twists both in the singles and in the ply of a doubled yarn.

The thermoplastic vinyl resin filaments may have any amount of stretching over 50%. Here- The heat may be applied in any suitable fashion to the bundle of vinyl resin filamentswhile his supported in such a manner as to prevent longitudinal contraction, Preferably a fiuid heat transfer medium is employed. Such transfer medium is preferably inert with respect to the filamentary material, so that its sole function is v to transfer heat to effect the fusion of the filamonofils after cooling may be removed, such as by wiping or squeegeeing.

It has further been found that the fusion into the form of monofils may be performed upon the twisted bundles of thermoplastic filaments while they are wound upon spools, bobbins, or in similar package form. Surprisingly, the fusion can be performed in the form of a package without causing the several convolutions of fused yarns to adhere together. In addition, the monofils thus produced are characterized by remarkable uniformity, high strength and elongation. The package form serves to prevent substantially all longitudinal contraction of the filamentary material wound thereon. As in the case of treatment of a non-packaged bundle, any contraction that takes place in the diameter of the bundle is so slight as to be hardly detectable.

Regardless of whether the bundle is treated in .the form of an unwound yarn or in package form, the twist apparently accounts for the remarkable uniformity of diameter along the length of the monofil and apparently causes the heat transfer medium to be substantially excluded from the interior of the monfil. This latter characteristic permits of easy removal of the heat transfer medium, such as by wiping. It is thought that the internal forces present in the stretched filaments being prevented from longitudinally shrinking the yarn when in the heating medium, and the thermoplasticity of the yarn are responsible for the fusing together of the filaments within a given bundle to produce a monofil without concomitant fusings of the several windings of the filamentary bundle upon the package. It should be understood, however, that the invention is not to be limited to any particular theory of operation.

Th following examples are illustrative of the invention:

Example 1 stantially the same as those of the unfused yam.

Example 2 A thread was formed of two ends of 40/46of the same poly-vinyl resin as that of Example 1.

The singles were oppositely twisted, each with 3 turns per inch and were doubled with 9 turns per inch S-twist in the ply. The thread was converted to a mono-filament by treatment with hot air.

Example 3 20 ends of 160 denier yarn of the same resin as that of Example 1, to which a 900% stretch had been previously applied, were plied with 3 turns per inch twist. 5 ends of this plied cord were then combined with 6 turns per inch twist. After heat treatment this cord resulted in a mono-filament of approximately 1*; of an inch in diameter.

As described above. the invention is concerned most particularly with the formation of monofils having a circular cross-section. However, any of the devices known in the art may be employed to impart any other cross-sectional shape to the monofil that may be desired. The monofils are applicable to the manufacture of hosiery,

tennis rackets, bristles, violin strings, artificial horsehair, etc.

While a preferred embodiment of the invention has been disclosed, the description isintended to be illustrative only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the invention as defined by the appended claims.

What I claim is:

1. In the method of forming a unitary filament from a bundle comprising thermoplastic vinyl resin filaments stretched in excess of 50%, the steps of twisting said bundle and effecting fusion of said filamentary material into a unitary filament by heating said bundle while preventing longitudinal contraction thereof.

2. In the method of forming a unitary filament from a bundle com-prising thermoplastic vinyl resin filaments stretched in excess of 50%,

the steps of twisting said bundle and effecting fusion of said filamentary material into a unitary filament by heating said bundle in the presence of an inert fluid while preventing longitudinal contraction thereof.

3. In the method of forming a unitary filament from a bundle comprising filaments of a thermoplastic copolymer, of vinyl chloride and vinyl acetate having a stretch in excess of 50%, the steps of twisting said bundle and effecting fusion of said filamentary bundle into a unitary filament by heating said bundle in the presence of an inert fluid while preventing longitudinal contraction thereof.

4. In the method of forming a unitary filament from a bundle comprising thermoplastic vinyl resin filaments having a stretch in excess of 50%, the steps of twistingsaid bundle and effecting fusion of said bundle into a unitary filament by heating said bundle in an atmosphere of live steam while preventing longitudinal contraction thereof.

5. In the method of forming a unitary filament from a bundle comprising thermoplastic vinyl resin filaments having a stretch in excess of 50%, the steps of twisting said bundle and effecting fusion of said bundle into a unitary filament by heating said bundle in glycerine while preventing longitudinal contraction thereof.

6. In the method of forming a unitary filament from a bundle comprising thermoplastic vinyl resin filaments having a stretch in excess of 50%, the steps of imparting a twist to the filaments in said bundle, winding said twisted bundle in the form of a'package and effecting fusion of said bundle into a unitary filament by heating said package in the presence of an inert fluid.

7. In the method of forming a unitary filament from a bundle comprising filaments of a thermoplastic copolymer of vinyl chloride and vinyl acetate having a stretch in excess of 50%, the steps of imparting a twist to said bundle, and effecting fusionof said bundle into a unitary filament by heating said bundle in an atmosphere of live steam while preventing longitudinal contraction thereof.

8. In the method of forming a, unitary filament from a bundle comprising filaments of a thermoplastic copolymer of vinyl chloride and vinyl acetatehaving a stretch in excess of 50%, the steps of imparting a twist to said bundle, and effecting fusion of said bundle into a unitary filament by heating said bundle in glycerine while preventing longitudinal contraction thereof.

9. In the method of forming a unitary filament from a bundle comprising filaments of a thermoplastic copolymer of vinyl chloride and vinyl acetate having a stretch in excess of 50%, the steps of imparting a twist to said bundle, winding said twisted bundle in the form of a package and effecting fusion of said bundle into a unitary filament by heating said package in the presence of an inert fluid.

10. In the method of forming a unitary filament from a bundle comprising filaments of a thermoplastic copolymer of vinyl chloride and vinyl acetate having a stretch in excess of 50%, the steps of imparting a twist to said bundle, winding said twisted bundle in the form of a package and effecting fusion of said bundle into a unitary filament by heating said package in an atmosphere of live steam.

11. In the method of forming a unitary filamerit, from a bundle comprising'filaments of a thermoplastic copolymer of vinyl chloride and vinyl acetate having a stretch in excess of 50%,

the steps of imparting a twist to said bundle,.

winding said twisted bundle in the form of a package and effecting fusion of said bundle into a unitary filament by heating said package in glycerine.

12. A method of forming a unitary filament from a bundle comprising thermoplastic vinyl resin filaments having a stretch of the order of about 75% to 1000% comprising the steps of imparting atwist of the order of a fraction of one turn per inch to turns per inch to said bundle and effecting fusion of said bundle into a unitary filament by heating said bundle in the presence of an inert fluid while preventing longitudinal contraction thereof.

13. A method of forming a unitary filament from a bundle comprising thermoplastic vinyl resin filaments having a stretch of the order of about 75% to 1000% comprising the steps of imparting a twist of 3 to 10 turns per inch to said bundle and effecting fusion of said bundle into a unitary filament by healing said bundle in the presence of an inert fluid while preventing longitudinal contraction thereof.

14. A method of forming a unitary filament from a bundle comprising thermoplastic vinyl presence of an inert fluid.

15. A method of forming a unitary filament from a bundle comprising thermoplastic vinyl resin filaments having a stretch of the order of about to 1000% comprising the steps of imparting a. twist of about 3 to 10 turns per inch to said bundle, winding said twisted bundle in the form of a package and effecting fusion of said bundieinto a unitary filament by heating said package in the presence of an inert fluid.

16. A method of forming a unitary filament from a bundle comprising filaments of a thermoplastic copolymer of vinyl chloride and vinyl acetate having a stretch of the order of about 75% to 1000% comprising the steps of imparting a twist of the order of a fraction of one turn per inch to 15 turns per inch tov said bundle and effecting fusion of said bundle into a unitary filament by heating said bundle in the presence of an inert fluid while preventing longitudinal contraction thereof.

17. A method of forming a unitary filament from a bundle comprising filaments of a thermoplastic copolymer of vinyl chloride and vinyl acetate having a stretch of the order of about 75% to 1000% comprising the steps of imparting a twist of about 3 to 10 turns'per inch to said bundle and effecting fusion of said bundle into a unitary filament by heating said bundle in the presence of an inert fiuid while preventing longitudinal contraction thereof.

18. A method of forming a unitary filament from a bundle comprising filaments of a thermoplastic copolymer of vinyl chloride and vinyl acetate having a stretch of the order of about 75% to 1000% comprising the steps of imparting a twist of about 3 to 10 turns per inch to said bundle, winding said twisted bundle in the form of a package and effecting fusion of said bundle into a unitary filament by heating said package in the presence of an inert fluid.

19. A method of forining a unitary filament from a bundle comprising filaments of a chlorinated thermoplastic copolymer of vinyl chloride and vinyl acetate having a stretch of about 75% to 1000% comprising the steps of imparting a twist of the order of a fraction of one turn per inch to 15 turns per inch to said bundle, winding said twisted bundle in the form of a package and effecting fusion of said bundle into a unitary filament by heating said package in the presence of an inert fluid.

KARL HEYMANN. 

